Real Gemstone vs Glass
Reviewed July 2026.
The fastest way to tell a real gemstone from glass is to combine hardness, temperature and internal features. Most real gemstones are hard (7+ on the Mohs scale) and scratch glass, feel cool and warm up slowly, and show natural inclusions, crystals or color zoning. Glass is softer, feels warmer to the touch, and often contains rounded gas bubbles, swirl or flow lines, and molded rather than crisply faceted edges — and glass 'gems' are usually suspiciously flawless and very cheap. No single test is proof, but per the GIA the reliable combination is a hardness check plus a loupe for gas bubbles plus the cool-touch test. When in doubt on a valuable piece, a gemologist confirms it.
Real gemstone vs Glass imitation, compared
| Real gemstone | Glass imitation | |
|---|---|---|
| Hardness (Mohs) | Usually 7+; scratches glass | Softer (~5.5); scratched by quartz or a steel file |
| Temperature | Feels cool, warms slowly | Feels warmer, warms quickly |
| Inclusions | Natural crystals, needles, color zoning | Rounded gas bubbles, swirl / flow lines |
| Facet edges | Crisp, sharp facet junctions | Rounded, molded or worn edges |
| Flaws & color | Some natural imperfections are normal | Often suspiciously flawless, perfectly even color |
| Price | Priced by rarity and quality | Very cheap |
Quick tells
- Rounded gas bubbles under a loupe = almost always glass.
- Warms up fast / feels warm to the touch = likely glass.
- Molded or rounded facet edges = glass; crisp sharp facets = cut stone.
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FAQ
- How can I tell if a gemstone is glass?
- Check hardness (most real gems scratch glass, glass doesn't scratch quartz), feel the temperature (real stones feel cooler and warm slowly), and loupe it for rounded gas bubbles and swirl lines — those bubbles are the classic sign of glass.
- Do real gemstones have bubbles?
- Generally no. Real gems have crystalline inclusions (needles, feathers, crystals), not the rounded spherical gas bubbles you see in glass and some synthetics. Round bubbles are a strong sign of glass or paste.
- Is glass ever used in real jewelry?
- Yes — 'paste' and glass 'gems' have been set in costume and even antique jewelry for centuries. That doesn't make the setting fake, but the stone itself is glass and worth a fraction of a genuine gem.